Apparatus for forming helical gear wheel bodies from powder

ABSTRACT

The disclosure is of an apparatus for forming helical gear wheel bodies by compacting initially powdery materials in dies by pressure between punches, the dies having mould cavities with helical grooves and there being positive controlled rotation of the dies and punches in relation to one another during the compaction and ejection operations by hydraulic or pneumatic systems including sensing means and drive means.

United States Patent Martin 1 51 July 18, 1972 [54] APPARATUS FOR FORMING HELICAL 1 References Cited GEAR WHEEL BODIES FROM POWDER UNITED STATES PATENTS [72] Inventor: Anthony Michael Ma -tin, El G bl 2,561,735 7/1951 Haller ..18/l6.5 Beechwood Av Lim ch lf m 3,394,432 7/1968 Laurent ..l8/l 6.5 Buckinghamshire, E a 1,958,199 5/1934 Morin ...18/l6.5 ux [22] Filed: Feb 2 1970 2,404,631 7/1946 Gronemeyer ..l8/l6 R 21 APPL .7864 Primary Examiner-J. Howard Flint, Jr.

Attorney-Cushman, Darby & Cushman [30] Foreign Application Priority Data ABSTRACT Feb. 1, 1969 Great Britain ..'.5,559/69 The disclosure is of an apparatus for forming helieal g wheel bodies by compacting initially powdery materials in dies 52 us. c1 ..425/78, 264/1 11 415/418 by mess"re between dies having cavities 511 int. c1. .3301) 3/06 1350b 11/14 with helical and being 1mm: 58 Field of Search ..249/s9- 18/2 is 16 R s F dies and Punches anmh" during the compaction and ejection operations [by hydraulic or pneumatic systems including sensing means and drive means.

3 Claims, 1 Drawing Figure INTRODUCTION AND BACKGROUND OF THE INVENTION This invention relates to an apparatus for forming helical gear wheel bodies by compacting initially powdery materials in dies by pressure between two punches.

It is well known that metals and other materials can be in troduced in powdery form into dies and there compacted by pressure between two punches to constitute coherent bodies, and these bodies may if required be subjected to further treatments, for example sintering. Bodies of a wide range of shapes can be satisfactorily formed thus, but hitherto owing to various factors such as the necessary compaction pressures and difficulties during ejection of the compacted bodies from the dies it has not been economically feasible to manufacture helical gear wheel bodies in this way.

The present invention is therefore intended to provide an improved apparatus for forming helical gear wheel bodies by compacting initially powdery materials in dies by pressure between two punches.

BRIEF SUMMARY OF THE INVENTION The invention comprises the provision of apparatus for effecting a method of fomiing a gear wheel body with helical teeth, comprising in combination a die and two punches between which the material is pressed and compacted in the die, characterized in that the said die has a female mould cavity with helical grooves for the formation of said helical teeth, that at least one of the said two punches is of male helicallytoothed form to match the said mould cavity and is arranged to move axially within and relatively to the die during the compaction of the material and during the ejection of the formed gear wheel body from the die, and that the apparatus further comprises a hydraulic or pneumatic system including sensing means and drive means such that the said one punch is positively driven in rotation relative to the die and that the said rotation is compatible and proportional with respect to the axial movement of the said one punch within and relative to the die and with the male helically-Toothed form of the said one punch fitting and matching in the said mouldcavity with helical grooves. In a convenient construction the apparatus comprises the said helically-grooved die, an upper punch, a lower helically-toothed punch adapted to enter said die with axial and rotational motion relative to the die, a powder-compacting press rig including said die and said upper punch and said lower punch, and the said hydraulic or pneumatic system whereby the lower punch is positively driven in rotation as above specified.

FURTHER DESCRIPTION AND ADVANTAGES OF THE INVENTION The said hydraulic or pneumatic system preferably comprises or consists substantially of the components of a standard lathe copying attachment. Advantageously the said one punch is shaped so that the gear wheel body and the said one punch are formed with inter-engaging projections and recesses whereby during ejection from the die the gear wheel body is positively driven in rotation by and in unison with the said one punch relative to the die.

Further features of the invention and how it may be put into practice appear from the following description and the accompanying drawing, in which some parts of an apparatus in accordance with the invention are illustrated diagrammatically and by way of example.

BRIEF DESCRIPTION OF THE VIEW IN THE DRAWING The single view in the drawing is a diagrammatic view showing partly in sectional elevation some of the parts of a conventional powder-compaction press rig and some parts of a preferred apparatus in accordance with the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring to the drawing, the apparatus comprises an internally helically-grooved die 1 in which the bore is fashioned to produce a female mould cavity with helical grooves for the formation of a gear wheel body with helical teeth. If material initially in the form of metal powder is suitably compacted within such a die, the product will be .a male gear wheel body B with helical teeth.

The die 1 is clamped securely within a die bolster 2 by means of a clamping ring 15 and screws 16.

Shown entered into the die 1 are a lower punch 3 and an upper punch 14, each of which has a male external helical gear form to match the female helical gear form mould cavity in the die 1. The material has been compacted by pressure between the two punches 3 and 14 to form the gear wheel body B.

For satisfactory production of gear wheel bodies it is necessary to control the movements of the lower punch 3 in relation to the die 1 during all compacting and ejection operations. For this purpose there is employed a method of and system for achieving this control as firrther described below.

On the lower punch 3 is an integral or rigidly-secured coaxial gear wheel 3A with an external plain gear form. The lower punch 3 with its gear wheel 3A :is supported on a lower punch support plate 4, which in turn is guided and supported on its periphery by a ball-bearing l7 and further supported by a thrust ball-bearing 5 carried on a lower punch adaptor 6, which is secured to a lower punch support plate or a lower press ram 7 of a substantially conventional powder-compacting press rig.

Situated on the underside of the die bolster 2 is a bracket 8, carrying a template or cam 9, which is preformed with a contour suited to control the rotations of the lower punch 3 during the operations of the apparatus. Mounted in the vicinity of the template or cam 9 is a slave cylinder 10 of a standard lathe copying attachment. A probe or stylus 10A of the cylinder 10 engages the template or earn 9. It is well known in the engineen'ng world that so-called lathe copying can be easily achieved by the use of a slave cylinder having a probe or stylus which follows the profile of a template or cam or a specimen component which is used as a master in conformity with which other components are to be manufactured. From the slave cylinder 10, a hydraulic or pneumatic system is connected by pipes to a conventional master pumping unit (not shown, but indicated by a chain-dotted line) from which is hydraulically or pneumatically pumped power to a main cylinder ll of the lathe copying attachment. It is known that whatever motion is given to the probe or stylus 10A of the slave cylinder 10 will be perfectly reproduced at the main cylinder 11, of which the output member or piston rod in lathe copying is usually connected directly to the tool holder.

In the present apparatus, however, to the output member or piston rod 11A of the main cylinder 11 is attached a toothed rack 12 with plain gear-form teeth which, by the movements of the rack 12, will rotate the lower punch 3, by the meshing of the rack 12 with the pinion or gear wheel 3A formed on the lower portion of the lower punch 3.

The operation of positively rotating the lower punch 3 in relation to the die bolster 2 and die 1 in any desired position in any desired speed is therefore simply achieved by controlling the rotational movements of the lower punch 3 by means of the lathe copying attachment with the aid of the preformed template or cam 9.

The cylinder 10 is mounted in fixed relationship to the lower punch support plate or lower press ram 7, and the template or cam 9 and the hydraulic or pneumatic system are such that the lower punch 3 is positively driven in rotation proportionally to its axial motion relative to the die 1 and in correct relau'onship to the helical formation of the meshing helical grooves and teeth during the compaction and ejection operations.

For many shapes of helical gear wheel bodies, for example were the depth of powder fill is comparatively shallow and the required body is fairly thin, there is no requirement that a top punch should enter the die 1 at any time, and it is sufficient if the top of the die 1 is closed (after filling with powder) with a solid flat-bottomed top or upper punch (not shown) which covers the die upper orifice and prevents powder from being ejected from the die 1 during the movements of the lower punch 3 and/or the die 1 during compaction.

In other cases, however, where the depth of fill is particularly long, or the gear wheel bodies to be produced are quite long, it may be necessary to have as shown in the drawing an upper punch 14 with an external helical gear formation such that the upper punch 14 is capable of entering and fitting into the die 1. In this case the upper punch 14 is suitably positively driven in rotation in relation to the die 1 like the lower punch 3, the positive rotation of the upper punch 14 being achieved with a separate or second set of slave and main cylinders of a separate or second lathe copying attachment (not shown).

Furthermore, for some purposes it may be necessary to rotate the die 1 during pressing operations, and in such cases the die 1 could be positively rotated in a somewhat similar manner to that used for the bottom punch 3 by using a separate second or third slave cylinder and main cylinder of a second or third separate lathe copying attachment (not shown).

From the foregoing it will be seen that controlled positive rotational movements required to rotate punches within a helical gear form die can be achieved efficiently and economically with the aid of hydraulic or pneumatic system such as are employed in standard lathe copying attachments. It may be seen that the use of such means is not confined to any one particular type of press rig for powder-compaction.

For example, where the press motions involve the use of a fixed die with a moving lower punch for compaction and ejection with a moving upper punch for further compaction, the apparatus according to the invention can be used.

Likewise in those presses where the press motions involve the use of a fixed lower punch and a movable withdrawal die to achieve compaction and ejection, with a moving upper punch for ejection, apparatus according to the invention can be used, the die and/or the upper punch being positively driven in rotation relative to the fixed lower punch.

In those presses where a subtool consists of a die frame into which tooling is placed, it is possible to produce a master tool frame in which a variety of tools (i.e. dies and punches) can be used and in this case, it would only be necessary to exchange the tools and the templates or cams 9 to enable helical gear wheel bodies of different shapes to be manufactured.

Each compacted helical gear wheel body is preferably positively driven in rotation relative to the die 1 during ejection in unison with and by one or both of the punches by forming the gear wheel body and the lower punch and/or the upper punch with inter-engaging means such as projections and recesses.

Various other modifications may be introduced without departing from the invention which is based upon the idea of positively driving in rotation relative to one another during compaction and ejection operations at least one punch and one die for forming helical gear wheel bodies from initially powdery materials by compaction. Tests have indicated that by thus positively driving the punch or punches in controlled rotation relative to the die it is possible to manufacture helical gear wheel bodies successfully and economically, avoiding or reducing any adverse factors such as great friction or uneven compaction or high axial forces or stressing or fracturing of the fomied bodies, which factors have hitherto prevented this manufacture.

What is claimed is:

1. In an apparatus for compacting initially powdery material to form gear wheel bodies with helical teeth, including a powder-compacting press rig having a die bolster, a die having a cavity with a helical groove therein secured in said die bolster, a lower unch support below said die bolster, a rotatable lower puncli mounte on said lower punch support and having a helically-toothed form and extending into and matching with said cavity and helical groove therein, a gear wheel rigid with said lower punch and mechanism for effecting relative rotational motion of said die bolster and said lower punch support for relative axial motions of said die and said lower punch in the axial direction of said lower punch, the improvement comprising that said punch-rotating means includes a cam secured to said die bolster, a hydraulic slave cylinder mounted in fixed relationship to said lower punch support, a slave piston in said slave cylinder, a cam-follower stylus secured to said slave piston and engaging said cam, a main hydraulic cylinder mounted in fixed relationship to said lower punch support, a main piston in said main hydraulic cylinder, a toothed rack secured to said main piston and meshing with said gear wheel, and a hydraulic system for moving said main piston proportionally to the movements of said slave piston, said punch-rotating means being arranged to effect positive rotation of said lower punch controlled in concord with the relative motions of said die and said lower punch in the axial direction of said lower punch and with passive matching of the helically-toothed form of said lower punch in said cavity and helical groove therein.

2. An apparatus according to claim 1, characterized in that the said one punch is shaped so that the gear wheel body and the said one punch are formed with inter-engaging projections and recesses whereby during ejection from the die the gear wheel body is positively driven in rotation by and in unison with the said one punch relative to the die.

3. The apparatus as recited in claim 1 further including a second punch with an external helical gear formation including an upper punch supported and rotated with respect to said die bolster by means identical to which said lower punch is supported and rotated with respect to said die bolster. 

1. In an apparatus for compacting initially powdery material to form gear wheel bodies with helical teeth, including a powdercompacting press rig having a die bolster, a die having a cavity with a helical groove therein secured in said die bolster, a lower punch support below said die bolster, a rotatable lower punch mounted on said lower punch support and having a helicallytoothed form and extending into and matching with said cavity and helical groove therein, a gear wheel rigid with said lower punch and mechanism for effecting relative rotational motion of said die bolster and said lower punch support for relative axial motions of said die and said lower punch in the axial direction of said lower punch, the improvement comprising that said punchrotating means includes a cam secured to said die bolster, a hydraulic slave cylinder mounted in fixed relationship to said lower punch support, a slave piston in said slave cylinder, a cam-follower stylus secured to said slave piston and engaging said cam, a main hydraulic cylinder mounted in fixed relationship to said lower punch support, a main piston in said main hydraulic cylinder, a toothed rack secured to said main piston and meshing with said gear wheel, and a hydraulic system for moving said main piston proportionally to the movements of said slave piston, said punch-rotating means being arranged to effect positive rotation of said lower punch controlled in concord with the relative motions of said die and said lower punch in the axial direction of said lower punch and with passive matching of the helicallytoothed form of said lower punch in said cavity and helical groove therein.
 2. An apparatus according to claim 1, characterized in that the said one punch is shaped so that the gear wheel body and the said one punch are formed with inter-engaging projections and recesses whereby during ejection from the die the gear wheel body is positively driven in rotation by and in unison with the said one punch relative to the die.
 3. The apparatus as recited in claim 1 further including a second punch with an external helical gear formation including an upper punch supported and rotated with respect to said die bolster by means identical to which said lower punch is supported and rotated with respect to said die bolster. 